content: /*
   * Copyright 2011-2016 David Karnok
   *
   * Licensed under the Apache License, Version 2.0 (the "License");
   * you may not use this file except in compliance with the License.
   * You may obtain a copy of the License at
   *
   *     http://www.apache.org/licenses/LICENSE-2.0
   *
   * Unless required by applicable law or agreed to in writing, software
   * distributed under the License is distributed on an "AS IS" BASIS,
   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
   * See the License for the specific language governing permissions and
   * limitations under the License.
   */
  
  package ix;
  
  /**
   * An Iterable plus a key representing a group for the
   * operator {@code groupBy()}.
   *
   * @param <K> the key type
   * @param <V> the value type
   */
  public abstract class GroupedIx<K, V> extends Ix<V> {
  
      /**
       * The group key.
       */
      protected final K key;
  
      /**
       * Constructs a GroupedIx with the given group key.
       * @param key the group key
       */
      public GroupedIx(K key) {
          this.key = key;
      }
  
      /**
       * Returns this group's key.
       * @return the key
       */
      public final K key() {
          return key;
      }
  
  }
  